Changes in islet plasma membrane calcium-ATPase activity and isoform expression induced by insulin resistance

ALZUGARAY M.E.; GARCIA, M,E.; DEL ZOTTO, H.; RASCHIA, M; PALOMEQUE, J; ROSSI, J.P.F.C; GAGLAIRDINO, J.J.

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS

ELSEVIER SCIENCE INC

Lugar: NEW YORK; Año: 2009 vol. 490

0003-9861

We studied the effect of insulin resistance (IR) induced by administration of a fructose-rich diet (FRD) to normal Wistar rats for 21 days, upon islet plasma membrane calcium ATPases (PMCAs) and insulin secretion. FRD rats showed significantly higher triglyceride and insulin levels, insulin:glucose ratio and HOMAIR index than controls. FRD islets released significantly more insulin in response to glucose and showed (a) marked changes in PMCA isoform protein content (decreased PMCA 2 and increased PMCA 3), (b) a decrease in total PMCAs activity, and (c) higher levels of cytosolic calcium [Ca2+]i. The lower PMCAs activity with the resultant increase in [Ca2+]i would favor the compensatory greater release of insulin necessaryto cope with the IR state present in FRD rats and to maintain normal glucose homeostasis. Thus,changes in PMCAs activity and isoform expression play a modulatory role upon insulin secretion during long-term adaptation to an increased hormone demand.